Detection of citrate overdose in critically ill patients on citrate-anticoagulated venovenous haemofiltration: use of ionised and total/ionised calcium

Andries J. Bakker 1. , 1. , E. Christiaan Boerma 2. , 2. , Halbe Keidel 3. , 3. , Peter Kingma 4. , 4.  and Peter H.J. van der Voort 5. , 5.
  • 1. Department of Clinical Chemistry, Stichting Klinisch Chemisch Laboratorium, Leeuwarden, The Netherlands
  • 2. Department of Intensive Care Medicine, Medical Centre Leeuwarden, Leeuwarden, The Netherlands
  • 3. Department of Clinical Chemistry, Stichting Klinisch Chemisch Laboratorium, Leeuwarden, The Netherlands
  • 4. Department of Intensive Care Medicine, Medical Centre Leeuwarden, Leeuwarden, The Netherlands
  • 5. Department of Intensive Care Medicine, Medical Centre Leeuwarden, Leeuwarden, The Netherlands


Background: The objective of this study was to elucidate the most practical and effective laboratory measurement for monitoring citrate in critically ill patients undergoing citrate-anticoagulated continuous venovenous haemofiltration (CVVH).

Methods: This observational study was performed at the mixed medical and surgical intensive care unit of a regional teaching hospital. The study population comprised ten consecutive critically ill patients with acute renal failure and indication for haemofiltration with the use of regional anticoagulation with citrate. Serum samples for the measurement of citrate and total and ionised calcium were taken from the pre- and post-filter compartments and from the arterial circulation of patients during citrate-anticoagulated CVVH.

Results: Receiver operating characteristic (ROC) curve analysis showed that for detecting citrate overdose (defined as a citrate concentration >1.0mmol/L) the best cut-off limits for total/ionised calcium and ionised calcium were 2.1 and 0.8mmol/L, respectively. Sensitivity and specificity for the cut-off limit of 2.1 for total/ionised calcium were 89% and 100%, and 84% and 100%, respectively, for the cut-off limit of 0.8mmol/L for ionised calcium.

Conclusions: In patients without liver insufficiency, total/ionised calcium performed slightly better than ionised calcium in detecting elevated citrate concentrations. However, because of the simplicity of its measurement, ionised calcium is preferred. Measurement of citrate is not necessary.

Clin Chem Lab Med 2006;44:962–6.

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Clinical Chemistry and Laboratory Medicine ( CCLM) publishes articles on novel teaching and training methods applicable to laboratory medicine. CCLM welcomes contributions on the progress in fundamental and applied research and cutting-edge clinical laboratory medicine. It is one of the leading journals in the field, with an impact factor of over three. CCLM is the official journal of nine national clinical societies and associated with EFLM.